The laboratory has had a longstanding interest in insomnia. Last year a major study of the effectiveness and hazards of benzodiazepine use in insomniacs was completed. This year attention was directed to information processing and circadian rhythms in insomniacs. The data suggest that insomniacs may differ from non-complaining individuals in personality traits, cognitive style and temperature regulation. Insomniacs were found to have difficulty retrieving material already well known to them, although there may be no dificits in acquiring new matrial. They also had temperature curves similar to normals in phase, but about 0.4 F higher. Studies are currently under way to test the hypothesis that, because of heightened mental activity during sleep, insomniacs may perform differently in ability to perceive stimuli and acquire information while asleep.